The present invention relates to a method of fabricating a hollow recreational product, such as a racket or bat, the product being formed of glass fibre or carbon fibre or other fibre materials.
It is commonly known that conventional rackets or bats are usually made of solid wood. Later hollow aluminum racket bodies were developed because wooden products were more easily deformed, cracked and rather poor in applying impact forces. Later fibre materials were used for the fabrication of these products. However, in adopting fibre materials for the fabrication of such products, the weight of the products should correspond with a specific standard and the products thus made should also have considerable force of intensity to withstand the impact force produced at the time of hitting. Although the technology of using fibre or carbon fibre materials to make various rackets, bats, fishing rods or golf rods are very progressive, the designs in making various products still have to correspond to the requirements of each specific force of intensity and elasticity. Therefore, the fabrication process, design, etc., of various products cannot be interchangeable. Each design can only be applied for the design of individual models. As a great impact force will be produced at the head of the body of the product at the time of hitting, the hardness and the force of intensity of the body itself are extremely important. The present technique can only fabricate solid products of which their force of intensity is able to correspond to the required standard by means of having the interior of the rackets filled with polyurethane (PU) foaming body and their exterior layer wrapped up with fibre board. Such products will let the player enjoy a pleasant feeling at the time of playing. However, as its foaming filament body occupied a part of the weight of the racket, the thickness of its fibre layer had to be reduced to control the fixed weight of the racket and thus weakened its ability to apply a force of substantial magnitude. In view of these defects, a method of fabrication different from that of conventional products of this type is employed while using fibre or carbon fibre or any other fibre materials suitable for fabricating such products, so as to cater to the habit of the players.
The present invention relates to a method of fabricating hollow recreational products, such as a racket or bat made of fibre or carbon fibre or any fibre materials suitable for the said fabrication.
Fibre materials have long been adopted for the fabrication of various sporting goods, such as bats, rackets, fishing rods, golf rods, etc., to make a product which is higher in quality, lighter in weight and stronger. Usually, fibre materials are applied over a PU foaming body. However, products of this type have been found unable to cater to the habits of players and are not sufficiently strong. Previously, ordinary sporting goods products for contest purpose have usually been made of solid wood. However, they are found to be easily deformed and cracked. Moreover, it is also rather difficult to obtain wood materials which are high in quality. Consequently, their cost becomes high. Aluminum hollow rackets have recently been developed and are lighter in weight and stronger. Aluminum recreational products, such as bats, are particularly valued for producing a clear and crisp sound at the time of hitting to allow the players to enjoy a pleasant feeling, especially when a four-bagger is being scored. Because of this, many players favor aluminum bats. However, after the bats have been used for many times, the surface of the heads of such aluminum bats will become concaved or pitted as a result of the strong impact forces when hitting. Thus, bats have to be made in such a way that their hardness is rather high. Therefore, the vibrations produced in the bat at the instant the ball is hit will be directly conducted to the arm of the player. The magnitude of the vibrations will depend on the speed at which the pitcher throws the ball and the strength which is produced by the arm of the pitcher. Over time, the vibrations will cause damage to and eventually ruin the health of the player. A bat made of fibre materials has been successfully developed as a solution to this problem. As the interior of this fibre bat is filled with PU foaming agent, the body of the racket is provided with excellent elasticity and anti-bending intensity to the effect that no cracking will be occurred and a part of the vibration, produced at the time of hitting, will be absorbed by the racket, so that no serious sporting damage will be caused. However,. the structure of this kind of fibre bat typically includes a large diameter at its head and a handle extended therefrom having a circular tube of a smaller diameter. A great difference will also be found in the degree of curve at their juncture. Its present fabrication method provides several layers of straight-striped fibre woven board directly rolled and wrapped up on the filament mold of the foaming agent of the bat body. The fibre layers on the joining part of the handle and the head of the bat are likely to be concaved after repeated hitting. Cracking will usually occur on the joining part of the bat due to the fact that such joining part will form a concentrated point of stress caused by poor conduction of the vibration force of the fibre layers as a result of their being cracked and folded. It becomes the main factor which leads to the cracking of the bat. On the other hand, as the bat is a solid one made of PU foaming material, it is impossible to produce a clear and crisp sound at the time of hitting. This makes the players rather unwilling to use it in their ball games. Therefore, it is quite impossible for the manufacturers to make a hollow bat due to the problems caused by the forementioned defects.
In view of the continual occurrence of these defects found in conventional bats, the inventor managed to successfully develop the rolling/covering method of fabrication first initiated by him, in which a hollow bat is made by having the mounting process of the fibre sleeve tube coupled with the mode of cutting of fibre woven board. In the process of fabrication, adhesive agents are filled into the bat body and the segments of the air blowing tube are adhered to the interior wall of the racket body, where the air is to be expelled at the time of heating, so as to prevent cracking from happening on the head or tail of the racket.
In a preferred embodiment according to the present invention, there is provided a method of fabricating a hollow recreational product having a head and formed of discrete layers of fiber material comprising the steps of providing a first fibre sleeve tube about an elongated tubular mold of the product, providing several discrete layers of overlapping fibre woven boards having lengths approximately equal to that of the length of the product, rolling the fibre woven boards about the fibre sleeve tube, providing a plurality of discrete layers of fibre woven boards shorter in length than the length of the product, rolling these short layers about the head of the product, mounting a second fibre sleeve tube about the outermost layer of rolled fibre Woven boards, sealing the head of the product with a fibre material, removing the mold from within the first tube to form a hollow product, inserting an air blowing tube into the hollow product, blowing air into the tube to pressurize the product, inserting the product into a die and heating the product within the die so as to harden and form a hollow product formed of fibre material.